Biocidal elastomeric compositions

ABSTRACT

A VULCANIZED ELASTOMERIC COMPOSITION COMPRISING AN ORGANIC ELASTOMER, AN ORGANIC TOXICANT DISSOLVED THEREIN, AND SELECTED PROPORTIONS OF COMPOUNDING INGREGIENTS INCLUDING CARBON BLACK, WAX, FILLERS, ETC,. AND VULCANIZED TO AN INTERMEDIATE DEGREE ARE BIOCIDAL MATERIALS HAVING A LOW, CONTROLLED AND TAILOR-MADE RATE OF TOXICANT RELEASE FOR LONG-EXTENDED BIOCIDAL ACTIVITY. ORGANIC ELASTOMERS EMPLOYED ARE NATURAL RUBBER, NEOPRENE, NITRILE RUBBERS, BUTYL, SBR, POLYBUTADIENE, ETC. ORGANIC TOXICANTS APPRECIABLY SOLUBLE IN SUCH ELASTOMERIC COMPOSITION FOR SUCH USE INCLUDE THE ORGANO-TIN COMPOUNDS, NITROSALICYLANILIDE COMPOUNDS, CHLORINATED HYDROCARBONS, ORGANO-PHOSPHOROUS COMPOUNDS, ETC. SUCH COMPOSITIONS ARE USEFUL IN SHEET-LIKE COVERINGS THICKER THAN ABOUT 0.05 INCH FOR ANTIFOULING PROTECTION OF SUBMERGED MARINE STRUCTURES; AS LARVACIDES IN THE FORM OF PELLETS, CHUNKS, SHEETS, STRIPS, TAPES, ETC., WHICH ON IMMERSION IN INFESTED WATER OR AIR LIBERATE TOXICANT KILLING THE ADULT, LARVAE AND EGG FORMS OF MOSQUITOS, MIDGES, BLACK FLIES, SCHISTOSOME CERCARIAE AND THEIR SNAIL HOSTS, OTHER GASTROPODS, AND AND OTHER DISEASE-CAUSING AND/OR DISEASE TRANSMITTING ORGANISMS AND INSECT PESTS; AS BACTERIOCIDAL, FUNGICIDAL AND ALGICIDAL SURFACES AND COVERINGS; AND AN ANIMAL- AND INSECT-REPELLANTS. CERTAIN INGREDIENTS OF ELASTOMER AND VULCANIZABLE RUBBER COMPOSITIONS, NOTABLY FATTY ACID MATERIALS, VERY MATERIALLY ENHANCE BIOCIDAL EFFICIENCY OF COMPOSITIONS CONTAINING THE ORGANO-TIN COMPOUNDS.

liifi lii alil 3,639,583 BIOCIDAL ELASTOMERIC COMPOSITiONS Nathan F.Cardarelli', Copley, and Harry F. Neff, Medina, Ohio, assignors to TheB. F. Goodrich Company, New York, N.Y.

No Drawing. Continuation-impart of application Ser. No. 515,154, Dec.20, 1965. This application June 28, 1968, Ser. No. 741,223

Int. Cl. A01m 9/38; A61k 27/12 US. Cl. 424125 Claims ABSTRACT OF THEDISCLOSURE pounds, nitrosalicylanilide compounds, chlorinatedhydrocarbons, organo-phosphorous compounds, etc. Such compositions areuseful in sheet-like coverings thicker than about 0.05 inch forantifouling protection of submerged marine structures; as larvacides inthe form of pellets, chunks, sheets, strips, tapes, etc., which onimmersion in infested water or air liberate toxicant killing the adult,larvae and egg forms of mosquitos, midges, black flies, schistosomecercariae and their snail hosts, other gastropods, and otherdisease-causing and/or disease transmitting organisms and insect pests;as bacteriocidal, fungicidal and algicidal surfaces and coverings; andan animaland insect-repellants. Certain ingredients of elastomer andvulcanizable rubber compositions, notably fatty acid materials, verymaterially enhance biocidal efficiency of com positions containing theorgano-tin compounds.

CROSS REFERENCES TO RELATED APPLICATIONS Th s application is acontinuation-in-part of applicants co-pending application, U.S. Ser. No.515,154, now abandoned, filed Dec. 20, 1965 and of the co-pending soleapplication of Nathan F. Cardarelli, U.S. Ser. No. 616,-

187 filed Feb. 15, 1967, now US. Pat. No. 3,417,181, the

latter being a continuation-in-part of the earlier applicaton Ser. No.528,785, filed Feb. 21, 1965, now abandoned. The present application isdrawn to biocidal elastomeric compositions whereas Ser. No. 616,187 isdrawn to a method of employing certain biocidal elastomeric compositionsin combatting certain disease-transmitting and disease-causingwater-borne organisms.

SUMMARY OF THE INVENTION ized rubber matrix specially compounded andcured in such a fashion that such toxicant remains soluble andsufficiently mobile in the matrix as to diffuse to the surface 3,639,583Patented Feb. 1, 1972 BACKGROUND OF THE INVENTION One of mans moreancient technical problems has been in retarding the growth of marineorganisms on sea water immersed objects such as ship hulls, docks,piers, buoys, etc., and the cleaning or removal of incrustations ofthese and other marine fouling genera. Until the early part of thiscentury, practical antifouling techniques had not varied appreciablysince the Phoenicians and their contemporaries discovered that foulingof ship bottoms is retarded by cladding ship hulls in copper sheets, orby paints containing salts or compounds of copper, mercury or arsenicwhich poison some of the more objectionable fouling genera. Even at thistime marine fouling is a national burden estimated to cost the nationabout 700 million dollars a year.

Certain organotin compounds which are toxic or repellent to a very widespectrum or marine fouling or ganisms have recently been proposed as apoisonous additive in acrylic and vinyl polymer paint vehicles to povide improved antifouling paints. Even though these vehicles are knownto possess excellent resistance to chemical degradation in sea water,the organotin toxicants are insoluble in them and are rapidly dissipatedfrom the immersed paint coating so that the effective life of suchimproved antifouling paints is about of the same order as other olderantifouling paints with less effective toxicants.

In more recent years, the efforts to retard marine fouling still havebeen focused on the development of im proved paint vehicles fordispersing the familiar copper, mercury, organotin and arsenic compoundsor other known antifoulin g toxic chemicals. All known antifouling paintcompositions function through leaching or exfoliating mechanisms. Theleaching types depend upon porosity in the paint coating to make freshtoxicant available with the result that very, very high toxicantloadings need be employed for any significant useful service life, forex-= ample, loadings of cuprous oxide of /wt. or more and loadings of 30to,40%/wt. 'or organotin type toxicants are commonly employed.Similarly, exfoliating type paints function by a sloughing off orchipping away of the surface of the paint film so as to expose freshantifoulant material. X-ray diffraction analysis of the leaching typepaint films shows that a toxicant gradient exists in the paint film.Antifouling efficiency aside, many of the known antifoulant paintsbecause of their necessary porosity or exfoliation behavior and hightoxicant loadings, inherently lack durability and integrity as paints.As a result, even though organotin type toxicants are known to be highlytoxic to a very wide spectrum of marine fouling organisms, theireffective toxic life in even the best vinyl and acrylic polymer paintvehicles is of necessity limited, as indicated above.

People by the millions suffer and die each year from malaria, yellowfever, schistosomiasis and similar dread diseases caused by or spread bywater-spawned or watercarried organisms. While numerous toxicants areknown for killing these disease-causing and disease-propagatingorganisms, there are many reasons why their use has not lead to theelimination of these dread diseases. For example, the use of DDT againstthe mosquito has not been too effective because of great expense,limited effective life requiring frequent re-applications, thedevelopment of DDT-resistant strains of mosquito, and widespreadcontroversy over real or imaginary toxic effects on human and otheranimal and vegetable life, particularly on our wild animals, birds andfish. By and large, these pests have been combatted by directapplication to the infested water of the pure toxicant or of thetoxicant on or in a diluent carrier. This has resulted in very limitedperiods of effectiveness (i.e. measured in from days up to 6 weeks instagnant water; much less in even slowly flowing water) necessitatingfrequent re-application. DDT, oils and other mosquito larvacides areapplied as often as twelve times a year in some areas of the southernUnited States. Applied in this fashion over any period of years, thetotal dosage of toxicant is enormous and never 100% effective. Also,direct application of toxicant may lead to at least temporary high localconcentrations due to poor dispersion, which concentration can be verytoxic to other forms of life. This is also highly inefficient andwasteful since many of the best toxicants have very limited solubilityin water (i.e. below about 50 ppm. by weight) and their lethallarvacidal levels are at least a decade or two below water solubilitylevels.

Also, conventional larvacides or insecticides such as DDT, theorgano-phosphates, arsenic, etc., are very dangerous to store,distribute and prepare and handle for application since in the formhandled, the toxicant concentration often is very high. DDT, malathion,parathion, etc., on finely-divided inert-type carriers, for example, arevery dusty and mobile and there have been horrible instances of multiplehuman deaths traceable to foodstuff contamination in warehouses. Also asindicated previously, these known toxicants must be used with great careand by skillful people to avoid poisoning of the application personneland of water (i.e. poisoning to the extent it would be unfit anddangerous for use by humans, cattle, fish and other desirable marine andbird life). Oiling a stagnant pond or swamp to kill mosquito larvae maybe effective against the larvae for as much as three to six months butthe usefulness of the water as a source of potable water for humans andanimals and the use of the pond for fish or recreation may be impairedfor much longer periods. Such treatment on moving water is ineffective.

Certain nitrosalicylanilide compounds, particularly the alkanolaminesalts of nitrosalicylanilides, have been established as highly effectivegastropodicides effective against schistosome cercariae (and otherfiukes") and their snail hosts. Limited use has been made of thesevaluable toxicants in combatting the dread debilitating and killerdisease of schistomiasis because of the expense of application andlimited period of effectiveness when the toxicant is directly meteredinto infested water. Once such addition ceases, the snail populationsoon recovers to its original density since a certain proportion of thesnail population is always out of water. As a result, schistosomiasis isthe worlds second worst killer disease estimated to kill about sixmillion peopleper year in the world and impair the efficiency of as manyas 200 to 300 million people at a time. Puerto Rico, in spite ofintensive public health measures, is estimated at times to sufferinfection of one in ten of its population. Infection is estimated toreach 75% of total population in some less-developed countries.Schistosomiasis is especially high in children because of theirproclivity for swimming in infested Waters.

There is a great need, therefore, for improved biocidal compositionswhich are safer, more efficient, longer-lived, capable of morecontrolled application, and which can be stored, handled and appliedeffectively and safely by less skillful people.

DESCRIPTION OF THE INVENTION According to this invention, we havediscovered that a vulcanized or cured elastomeric composition based onan organic, vulcanizable elastomer containing a biocidal organictoxicant dissolved therein and compounded and cured so as to exhibitcontrolled release of the toxicant are a unique class of materialscapable of numerous 4 biocidal applications such as long-livedantifouling coatings and sheathings on marine surfaces, as larvacidaland insecticidal carriers which effect on immersion in air and watermolecular release of the organic toxicant into the air, water, or otherenvironment at controlled rates thereby making it possible to maintainin such environment the lowest lethal biocidal levels over very longperiods, as animal and insect repellant surfaces and coatings, and asbacteriostatic, fungicidal, and algicidal coatings or sur faces equallyeffective for long periods.

More specifically, the biocidal elastomeric compositions of thisinvention are special rubbery compositions in which both theconcentration of biocidal toxicant dissolved therein, on the one hand,and the proportion of certain types of compounding ingredients and thestate of cure or vulcanization on the other, are balanced or adjusted,as to provide, when vulcanized, a rubbery elastic matrix in which theorganic toxicant remains appreciably soluble and sufficiently mobile asto diffuse to the surface of the composition at a rate at which it isremoved from the surface and which is finite, low and selected for theintended biocidal application. Such surface toxicant is released to theenvironment, particularly in water, by molecular release.

The release of toxicant by molecular release is by far the mostefiicient in a statistical and biocidal sense and, with the biocidalrubbers of this invention, usually, is several orders of magnitudeslower than any other known release mechanism. Prior art methodsinvolving direct application of the pure or merely physically-dilutedforms of toxicants such as, for example, in the form of fog-likedroplets of toxicants most of the effective agent in the droplet isunavailable and, statistically, the chances of direct contact of thedroplet with the target pest are low. Much lower concentrations of thesame toxicant released over longer periods by molecular release puts thereleased toxicant to work at the desired interface in its most activeand economical form.

Molecular release at low levels by means of these bio cidal rubbers maypermit the use of many organic toxicants of known high biocidalactivity, but which are known to hydrolyze or oxidize or which areeasily absorbed or destroyed too rapidly to be useful for direct ap--plication. The rubber matrix holds such materials in solu tion andprotects such toxicants until after release and, even though thebiocidal activity of released material quicklv dissipates, such isquickly renewed and sustained over long periods.

Molecular release of toxicant also permits for the first time a new andpractical type of attack on many types of disease-causing and/ordisease-transmitting pests. Hereto fore, many of such pests such asmosquitos, midges, flies. schistosome cercariae, etc, have been attackedin the adult or larvae forms of the host pest employing the largedosages of toxicants required. We have found that toxicants in dissolvedmolecular form are capable of killing the very young pest or larva formthereof and often preventing the hatching of the eggs of the same pestsat concentrations one or two decades or more below the concentrationsrequired for the more adult form of the same pest. In the case ofschistosome cercariae and their snail:

hosts, we have found that the snail is very difiicult to kill whereasthe actual disease vector, schistosome cer cariae per se, are killed ina few minutes by organotin or nitrosalicylanilide type toxicants atconcentrations estimated to be of the order of a few p.p.b.(parts/wL/billion), whereas to kill the adult Australorbis and Japonicustype snail hosts requires contact of hours with concentrations up to 1ppm. (parts/wt./million) or more.

We have also observed that certain pests succumb or are irreparablyharmed on long-continued exposure to some well-known toxicants and atconcentrations so low as not previously thought fatal. For example,snails exposed to organotin compounds but counted as still alive or atleast not dead after the usual 24 hour observation period are found evenwhen placed in clean, non-toxic water eitherto die or remain moribundfor many days after exposure. It may be necessarv, therefore, toreassess the use of toxicants by measuring biocidal activity, not on the24 hour/ 100% kill basis now current, but on exposure for 7, or days andlonger and continuing the death count for at least an equal period oftime. Thus, since it EFFECT OF COMPOUNDING INGREDIENTS We have foundthat high structure (reinforcing) carbon blacks, petroleum waxes, andmany of the other filler and lubricant type of ingredients normallyadded in the compounding of rubber have the effect of reducing the rateof diffusion of organic toxicants dissolved in the vulcanized matrix. Ingeneral, the biocidal rubbers of this invention contain lower levels oftotal compounding ingredients than those commonly employed in the samebase elastomer intended for high-stress, non-biocidal applications ofthe rubber. For example, whereas 40 to 100 parts/ wt. or more of a highstructure carbon black per 100 parts/wt. of base elastomer (hereinafterphr.) commonly are utilized in such high-stress applications asautomobile tire treads, the compositions of this invention willgenerally be below this level of carbon black, although the levelrequired seems to be dependent mostly on the particular base elastomer,the degree of structure in the black itself, and the ability of thematrix to dissolve the particular toxicant in question. For example,neoprene rubber appears to require less carbon black for diffusioncontrol than most other rubbers. Carbon black levels of from about 5 toabout 35 phr. (more preferred from about 10 to about 35 phr.) seem toproduce a very wide range of release rate with neoprene. Naturalrubbers, SBR, nitrile rubbers and butyl rubbers, require somewhat morecarbon black for low release rates. From about 30 to about phr. seemrequired in the latter rubbers. EPDM rubber appears anomalous inrequiring very high carbon black levels of from about to about 100 phr.

Not all carbon blacks are effective in controlling toxicant diffusionfor we have found that only the higher structure carbon blacks (i.e.,having oil absorptivities of 9 gals./ 100 lbs. or more) are effective.With carbon blacks of lower oil absorptivity (i.e., lower structure) itis not ordinarily possible to achieve low toxicant release (diffusion)rates at practical carbon black loadings. With the formulations whichwould require the higher carbon black levels, the use of from about 1 toabout 7 phr. of petroleum wax is recommended since the proportion ofcarbon black can be reduced. It appears that with most elastomers andmost toxicants from 5 to about phr. of carbon black is a good practicaloperating range with from about 10 to about 55 phr. being morepreferred. Toxicant loadings above about 10 phr. will usually require atleast 20 phr. of carbon black and up to about 50 to 70 phr. for lowtoxicant release rates.

With the above proportions of carbon black and other compoundingingredients employed with most base rubbers, it follows that thebiocidal elastomeric compositions of this invention will have a specificgravity at 25 C. greater than about 1.0. In antifouling applications andin many other biocidal applications where the rubber is supported oremployed in an environment other than water, the effect of density ofthe rubber is of little moment.

However, in many larvicidal applications carried out in water, thesebiocidal compositions will sink and this is an advantage in destroyingsnails (which move throughout a body of water) and other scavenger orbottom-favoring 6 pests or larvae and in all larvicidal applicationscarried out in moving waters since the toxicant is and must be releasedthroughout the body of water to be effective in such applications.

When it is desired to employ a toxicant loading which is above theintrinsic solubility of the toxicant in the matrix and/or difficultiesin mixing are encountered due to such high toxicant loadings, a phenolic(i.e., phenol/formaldehyde) resin may be employed in the form ofmicroballoons or micro-spheres to absorb and hold the excess toxicant.From about 20%/wt. to about /wt. of the phenolic resin based on theweight of toxicant can be employed in this manner without undue loss ofvulcanizate physical properties and while otherwise control ling thetoxicant release rate. Even though bis(tributyl tin) oxide is soluble inneoprene rubber to the extent of only about 9 to 10%lwt. based on theraw rubber, the use of these amounts of microspheres makes it possibleto employ up to 15 phr. or more of TBTO in neoprene with very littleother changes in the recipe and with an effective biocidal l fe measuredin years.

As indicated, we have also found that petroleum waxes of the typenormally employed in rubber compounding for lubricity and antioxidantactivity have a relatively strong suppressing effect on toxicantdiffusion or toxicant release rate. However, one is limited in theproportion of wax that can be incorporated into rubber by ordinarymixing techniques to the range of up to 7 phr. The use of from about 1.5to about 5 phr. of such wax, in any given composition, will contributevery materially increased biocidal life to the composition. We prefer toemploy both carbon black and wax in any formulations in which very longbiocidal life is desired.

Other filler and/or lubricant-type compounding ingredients are of lessereffect than carbon black and wax but nevertheless reduce toxicantrelease at higher loadings and must be taken into account when designinga formulation. In general, total loadings, other than carbon black andwax, should be below about 20 phr.

We have also found that certain ingredients of sulfur vulcanizationsystems, notably the C to C fatty acids normally added as vulcanizationaccelerators and dispersants or normally present in the elastomer,apparently either react or cooperate in some manner with the organetintoxicants during vulcanization so that the biocidal activity andefiiciency of the composition is relatively greater than can beattributed to the amount of original toxicant added. We have found that,of the fatty acid materials, lauric acid, palmitic acid, and oleic acidare very effective, with palmitic acid having greatest apparentactivity. Laboratory bench scale tests have confirmed that bis-(tributyltin) oxide reacts with these fatty acids. From about 0.5 toabout 10 phr., more preferred from about 1 to about 8 phr., of thesefatty acids are useful to secure increased biocidal activity with theorganotin toxicants.

EFFECT OF STATE OF CURE Also, we have found that both the more highlyvulcanized biocidal rubbers and the corresponding unvulcanized formsthereof are of markedly lower biocidal effectiveness than are thespecimens cured to intermediate levels of cure. The reason for this isnot understood. Fortunately, high or highest biocidal activity for agiven composition usually is obtained at a state of cure not too farremoved from that known to produce optimum vulcanizate physicalproperties with the particular base rubber, compounding recipe and thevulcanization system employed. The state of cure is unaffected by thetoxicant so that known vulcanization systems, techniques and equipmentmay be employed in the known manner to obtain the desirable state ofcure for any given formulation.

The compositions of this invention may employ any of the knownvulcanization systems including all of the sulfur vulcanization types,metal oxide cures, peroxide cures, amine cures. etc. It is preferred, toemploy sulfur vulcanization systems because these are inexpensive, theyare simple and well understood, and appear to offer the most desirablebiocidal vulcanizates.

As between the effects of compounding ingredients and state of cure, theeffects of the former on toxicant release is the stronger and is moreeasily subject to greater variation.

ORGANIC TOXICANT By the term organic toxicant" is meant a toxicantcompound carrying in its chemical structure sufficient ofchemically-bound organic groups as to render the toxicant soluble to theextent of from about 0.02% to about wt. in the organic vulcanizableelastomer, as the latter is defined below. More preferred toxicantshave, in addition, low volatility in air and low solubility in naturalwaters. The toxicant should have a boiling point in excess of about 150C. and most preferably in excess of about 200 C.

The preferred toxicants should have a solubility in natural waters (i.e.water containing some hardness) below about 50 p.p.m., more preferablybelow about p.p.m., and most preferably not more than about 2 to 10p.p.m. The exact nature of the toxicant having these properties is nottoo important since the choice will be dictated primarily by the targetpest to be killed, controlled or repelled.

Particularly effective toxicants are the organotin compounds of theformula R SnX (see definition below), the nitrosalicylanilide compoundsand their salts, the Organophosphorous, and the chlorinatedhydrocarbons.

In the formula (R Sn),,X, n is a number from 1 to 3 I (intermediatenumbers indicate mixtures), R is an alkyl or aryl group and X is asubstituent radical selected from the class consisting of sulfide,oxide, halogen such as chloride, bromide, and fluoride, chromate,sulfate, nitrate, hydroxide, acetate, fatty acid groups such as acetate,octanoate, laurate, neodecanoate, rosinate (or resinate), dimethyldithiocarbamate, naphthenate, paravinyl benzoate, acrylate,methacrylate, iso-octylmercaptoacetate, hydride or methoxide. PreferredR groups are alkyl groups containing from 3 to 8 carbon atoms. The butylgroup seems to maximize toxicity of the tin compounds. Preferred Xgroups are oxide, sulfide or a halogen. A particularly effective memberof the latter preferred class is bis(tri-n-butyl tin) oxide (TBTO").Other highly effec tive compound is bis(tri-n-butyl tin) sulfide (TBTS)and tributyl tin fluoride (TBTF).

Typical examples of other organotin compounds useful A in the biocidalrubber compositions of this invention are bis(trin-propyl tin) oxide,tri-n-propyl tin chloride (TPTC"), triisopropyl tin chloride,bis(triamyl tin) oxide, triisobutyl tin chloride, tributyl tin acetate,tributyl tin chloride, triphenyl tin chloride, tributyl tin laurate,tributyl tin adipate (TBTAd), tributyl tin chromate bis- (tributyl tin)maleate, tributyl tin neodecanoate, bis-(trin-butyl tin) phthalate, amyldiethyl tin chloride, butyl dipropyl tin chloride, bis(tri-n-butyl tin)sulfate, phenyl dibutyl tin chloride, tributyl tin resinate (TBTR),tributyl tin isooctylmercaptoacetate, bis(tri-n-butyl tin) phosphite,triphenyl tin benzoate, tributyl tin dimethyl dithiocarbamate, the TBTOester of Z-mercaptobenzothiazole, tributyl tin naphthenate, and others.

Another highly preferred class of toxicants for use in the biocidalrubber compositions of this invention are the salicylanilides and theirderivatives including their alkalimetal and alkanol amine salts such asare described in US. Pats. 3,079,297, 3,113,067 and 3,238,098. Oneparticular toxicant of this class known commercially as Bayluscide" (TMBayer) has been found particularly effective in the biocidal rubbers ofthis invention. The latter material is said to be the Z-aminoethanolsalt of 5,2'-dichloro-4'-nitrosalicylanilide and has achieved at leastprovisionally acceptance by public health authorities in some countries.

The salicylanilide type toxicants most useful in the biocidal rubbers ofthis invention have the formula wherein R is hydrogen or a loweralkanoyl radical having 1 to 4 carbon atoms, R; is hydrogen or methyl, Ris a halogen such as chlorine, bromine or fluorine, R, and R arehydrogen, methyl, or a halogen, or a nitro group, R

R and R, are hydrogen, halogen or a nitro group and wherein always thecompound contains only one nitro group and at most three halogensubstituents.

Illustrative toxicants having the above fo mula are the alkali-metal andalkanolamine salts of the above and still other compounds of the aboveformula. Preferred nitrosalicylanilide compounds are the alkanolarninesalts.

Organo-phosphorous compounds which may be employed are Malathion (0,0dimethyl phosphorothioate or diethyl mercapto-succinate) (AmericanCyanamid Co.), Dasanit (Chemagro Corporation, Kansas City, Mo., asulfinyl phosphorothioate (C,H -,O) PSOC,H SOCH,); Dursban" (DowChemical Company, 0,0-diethyl-0,3,5,6-trichloro-Z-pyridyl-phosphorothioate); tributyl-tin phosphate; DBTP,bis(tributyl tin) phosphate; Abate,"0,0,0',O'-tetramethyl-0,0'-thiodi-p-phenylene phosphorothioate(Cyanamid); 0,0-bis(p-chlorophenyl)acetim idazolyl phosphoramidoiodate;tributyl phosphorothioate, Baytex (Chemagro Corp.,0,0-dimethyl-O-[(4-methylthio)-m-tolyl)Jphosphorodiate, and many others.

Chlorohydrocarbons such as Chlordane" (Vclsicol Chem. Corp.;octachloro-4,7, methano-tetrahydroindane); Heptachlor" (Vclsicol Chem.Corp.; heptachloro-4,7- methanotetrahydroindane); Dichlone" (AcetoChemical; 2,3-dichloro-1,4-naphthoquinone); Lindane (City Chemical;hexachlorocyclohexane); and many others.

The preferred organic toxicants for use in this invention are theorganotin compounds and the nitrosalicylanilide compounds.

TOXICANT CONCENTRATION In general, the biocidal rubber compositions maycontain anywhere between about 0.02 to about 20 parts/wt. of toxicantper parts/wt. of base elastomer in the composition (hereinafter phr.").Where the upper limit exceeds the intrinsic solubility of the toxicantin the base elastomer, slightly increased proportions of carbon black,wax and/or other fillers and special additives (phenolic resinmicro-spheres) can be employed to absorb and hold the excess toxicant.More practical concentrations are between about 0.2 to about 15 phr. oftoxicant and for longest-lived biocidal effects between about 4 andabout 12 phr. The concentration chosen will depend on the biocidalapplication and the biocidal longevity required. For antifoulingapplications of organotin toxicants, the concentration will usually bein the range of from about 1 to about 15 phr., with from about 4 to 12phr. being preferred. For larvacidal, algecidal, fungicidal andbacteriostatic applications the choice of concentration will coveralmost the entire range depending on the application, although agenerally effective range is from about 2 to about 12 phr.

Toxicant concentration can also be expressed in terms of the toxicantconcentration released to the environment. For example, Bayluscide issaid to exhibit a solubility in distilled water of 230 p.p.m.:SO (byweight) and less than this in hard waters. The organotin compoundsusually exhibit a solubility below 50 p.p.m. in natural waters. Asindicated, biocidally lethal concentrations usually are well below thewater solubility level.

ORGANIC ELASTOMER The term vulcanizable organic elastomer means anyvulcanizable elastomer or rubbery material whose structural backboneconsists of carbon-to-carbon chains, although such structure may containnon-hydrocarbon substituents (i.e. halogen and nitrile groups) orpendant groups (as contrasted with a silicone rubber having a backboneof OSi--O repeating units); and which is vulcanizable or curable fromthe thermoplastic to the elastic condition.

By vulcanizable to an elastomeric condition is meant an ability of therubber to be converted from a thermoplastic to an essentially elasticcondition by any of the many mechanisms including, but not limited to,sulfurvulcanization, rnetal-oxide curing systems, peroxide curingsystems, amine curing systems, curing through metalcarboxylate linkages,and many others.

Thus, there may be utilized natural rubber, neoprene (polychloroprene)rubber; butyl (isobutylene/isoprene copolymer) rubber; SBR(styrene/butadiene rubbers); polybutadiene rubbers such ascis-polybutadiene rubber; synthetic polyisoprene rubbers such ascis-polyisoprene or synthetic natural rubber; nitrile rubbers(butadiene/ acrylonitrile c'opolymers); ethylene/propylene copolymerrubbers; EPDM rubbers (ethylene/propylene/dicyclopentadiene and otherethylene/propylene/diene terpolymers); and others.

The miscibility or solubility of the organic toxicants such as organotincompounds and nitrosalicylanilide toxicants in the above (raw oruncompounded) rubbers is appreciable, as will appear below:

1 Determined by a laboratory immersion procedure.

2 "TBIO is bis(tributyl tin) oxide.

3 Bayluscide a trademarked product of Farbenfabriken Bayer A.G., W.Germany distributed by Chemagro Corp. of Kansas City, Mo, and said to bethe 2-aminoethyl salt of 2',5-dichloro4-nitrosalicylanilide.

Butadiene/acrylonitrile copolymer rubbers oi indicated combined acryio(acrylonitrile) content.

It should be noted that except for certain of the nitriletype syntheticrubbers the solubility of these toxicants in all of the rubbers isbetween about 7% to about /wt. With the nitrile rubbers toxicantsolubility is adequate in the range of from about 15% to about 40% lwt.of combined acrylonitrile and rapidly decreases when the bound orcombined acrylonitrile content of the copolymer exceeds the region ofabout 40% wt.

The above and other similar elastomeric substances share commoncharacteristics such as ability to accept carbon blacks, waxes, andfatty acids, they are sulfurvulcanizable (although some respond also toother vulcanization systems), and they are strong and elastic whenvulcanized. The choice among the many rubbers available will be based oncost and factors other than biocidal efiiciency such as, for example,ability to resist environmental degradation, ease of application,essential physical properties required by the use, environment, etc.Pre- 10 ferred rubbers for compositions intended for antifoulingapplications in seawater are neoprene, natural rubber, butyl and thenitrile rubbers containing not more than about 35%/wt., of combinedacrylonitrile. Most preferred in compositions for use in antifoulingapplications is neoprene.

In biocidal rubber compositions, particularly for use in larvacidalapplications in fresh water, preferred rubbers are neoprene, naturalrubber, butyl rubber, SBR, and EPDM rubbers. Again, most preferred forthis type of application is neoprene.

PREPARATION OF COMPOSITIONS The compositions of these compositions maybe prepared ln conventional rubber mixing and processing equipment withonly slightly more careful precaution for ventilation, care againstdermal contact, etc. than are already I common in the rubber industry.In addition to the compounding ingredients referred to herein, thecompositions should also include antioxidants, lubricants, acceleratorsand curatives, and other ingredients used for quality rubbervulcanizates in accordance with the rubber compounders art. Theelastomer is mixed in the usual fashion with the'toxicant being added tothe mixing batch at the time for addition of similar non-toxic rubbercompounding ingredients. For example, the organotin com-- pounds aresupplied in the form of dry high melting powders which may be added atthe same time as other dry and powdery compounding ingredients.Toxicants which are liquid or oily in consistency are added in the samefashion and at the same point in the mixing operation as are theordinary lubricating and extender oils. Mixing may be carried out ontwo-roll rubber mills or in Banbury or other internal-type mixers. Oncemixed, the composition may be sheeted off on a rubber mill or on arubber calendar for use as sheets of anti-fouling rubber, or processedthrough an extruder as strips or tapes, or the output of the extruderfed to a pelletizer where it is cut, chopped or formed into pellets, orthe stock formed into crude sheets and/or preforms for use in moldinginto the shapes and forms desired. The so-shaped rubber can then bevulcanized in an air or steam oven before use. The unvulcanizedcomposition may be calendared or skim coated on fabric or othersubstrates to produce biocidal sheeting and fabrics for variousprotective uses.

Compositions for antifoulant use will usually be prepared as calendaredsheets of uniform gauge or as forma: ble putties which are then adheredby means of appropriate rubber-to-metal or other adhesives or,vulcanized directly to a variety of substrates such as metal plates,wood, plastics, fabrics, concrete, fiberglass and other structuralmaterials, or prevulcanized pieces of these compositions may be adheredto any of the foregoing substrates by suitable cements and adhesives.One particular advantage of the antifouling compositions of thisinvention is that antifouling protection is not their only advantage onsubmerged marine structures. Rudders, propellors, shafting, housing,etc., on ship hulls are completely protected against cavitation. Whenthe antifoulant layer is well adhered, metallic substrates are morecompletely protected against corrosion than when painted. Since the antifoulant rubber layer is thicker and heavier than a paint coating, itwill have antiresonant characteristics. Depending on convenience,vulcanization of the antifoulant rubber may be'etfected afterapplication by applying heat or by having incorporated therein so-calledroom temperature curing systems which cure slowly after application. Inuse of larvacides, the biocidal rubber is usually fabricated so as tohave a higher surface: volume ratio than obtains in antifoulantapplications and this factor will require adjustment in either theformulation or in the cure, or in both, to obtain a toxicant releaserate within the requirements of the particular larvacidal usecontemplated. When so adjusted, the biocidal rubber is particularlyeffective for the target larvae but is not harmful to other animal andvegetable 'life in the concentrations quired.

BIOCIDAL ACTIVITY The biocidal elastomeric compositions of the presentinvention have a wide spectrum of uses. For example, the surface ofsheets of these compositions thicker than about 0.05 inch adhered to amore or less imprevious substrate and immersed so one .surface onlycontacts sea water remain free of barnacles, bryozoans, hydroids, algae,bugula, mussels, tunicates and other fouling genera for periods up to50, 70 or 90 months. We have found that a minimum thickness forsingle-surface exposure is in the range of 0.05 inch and is necessaryfor long-lived antifouling action. When more than one surface is exposedto sea water, higher toxicant loadings, lower release rates, and thickerlayers (i.e. at least about 0.125 inch) are required. We consider thisthickness effect as the most convincing proof of the diffusionalmechanism believed responsible for the biocidal performance of ourbiocidal rubbers. It should be noted that 0.05 inch is at least severaltimes thicker than usually is obtainable with paints (0.008 to 0.02inch) by practical or economical application procedures and whileretaining adhesion of the paint film. Even better results are obtainedat thicknesses of 0.06 to 0.15 inch. It appears that the relativelythick layers of practical antifouling rubber (containing from about 3 toabout 12 phr. of organotin toxicant) constitutes an adequate reservoirof toxicant for very long life. Periodic chemical analysis of longimmersed samples confirm a slow decline in toxicant concentration.

A surprising and useful result of the compositions used as antifoulantlayers is the freedom of the immersed surfaces from algae. grasses andother slimy marine growths. Such accumulations do not occur or are nottenaciously retained until after the toxicant level of the rubber isexhausted and barnacles and other fouling genera begin to attachthemselves to the surface.

The biocidal rubber compositions of this invention containing alarvicidally-effective organic toxicant are extremely effectivelarvacides which require only immersion of a sufficient quantity ordosage of the rubber in the infested water of farms, ponds, ditches.swamps, rivers, or other water bodies to maintain therein low but lethalproportions of toxicant ranging from about 0.1 p.p.b. to 1 or 2 p.p.m.For example, organotin compounds such as bis(tri-n-butyl tin) oxide at alevel of from about 0.02 to %/wt. in a vulcanized rubber composition ofthis invention adjusted as indicated above and broadcast in pellet formon the infested water at a rate of from about 10 to lbs/acre of waterwill maintain the treated water free of live mosquito larvae for manymonths. Gravid female mosquitos are attracted to water treated in thisfashion with biocidal rubber containing organotin toxicants. At evenlower levels of toxicant, a very high proportion of the mosquito eggsfail to hatch. Such larvacidal effect is maintained for many months oreven years in stagnant water and has been observed to be maintained for9 months or more in running water.

Likewise, a similar formulation containing Bayluscide" (trademarkedproduct of Farbenfabriken Bayer, A.G.; the Z-amino-ethanol salt of2',5-dichloro-4'-nitrosalicylanilide) and employed in a similar fashion,will effect a 100% kill in 24 hours or less of shistosome cercariae andtheir snail hosts. Shistosome cerariae, per se, are killed in the matterof minutes after contacting water containing 1 p.p.b. or less ofBayluscide.

Surprisingly, Bayluscidc/rubber compositions of this invention areexcellent antifouling materials, although antifouling behavior of thistype of toxicant has not been reported previously.

Cir

Since the toxicant concentrations in these rubber compositions arefirmly bound and the composition in itself is relatively immobile,shipping, storage, and handling are a great deal safer than the puretoxicant alone and the health hazard from accidental ingestion bybreathing and/or by skin absorption greatly reduced. Even accidentalspillage is unlikely to lead to severe poisoning since release oftoxicant in this case is severely limited by low volatility and/or lowsolubility of the toxicant in air or water.

These compositio'ns may be employed in various forms for protectivebiocidal action. For example, water bags or canteens may be made offabric rubberized with one of these biocidal rubbers, or the canteenscan be molded directly of the rubber. In any case, these compositionswill be toxic to flukes and many other organisms in the water harmful tohumans. The compositions themselves are apparently not harmful to humansand do not materially affect the taste of water. Obviously, anycomposition touching food, water or other material for human consumptionmust in all other respect be based on toxicants non-toxic to humans.

Protective clothing made of fabrics rubberized with one of thesecompositions or impregnated with a latex of biocidal rubber can be madewhich will protect humans and animals against many insect pests and manyforms of bacteria and fungi. In screening new organic toxictants for usein biocidal rubber, failure of bacteria and fungi to multiply on thesurface of a vulcanized rubber composition containing it has been founda very useful and inexpensive research tool indicating the biocidaleffectiveness of the composition.

Some of the salient experimental facts we have confirmed using thebiocidal rubbers of this invention are:

(1) Rubber compositions containing organotin additives effect a kill(within 24 hours) of mosquito and midge larvae at less than 1 p.p.m.concentration in the infested water of the substance or substancesreleased by the rubber into the water, and their eggs fail to hatch ateven lower concentrations;

(2) The compositions of (1) effect a 100% kill of snail hosts ofshistosome cercariae at concentrations of less than 200 parts/wt. perbillion of the dissolving substance or substances in the infested water,within 24 hours of the immersion of the composition;

(3) The item (1) compositions effect a 100% kill of shistosome cercariaethemselves at concentrations of less than 1 p.p.b. of the dissolvingsubstance or substances in the infested Water within three minutes ofthe exposure of the cercariae, thereby indicating that infested Waterstreated with very low concentrations in the form of long-lastingbiocidal rubbers can free the water of cercariae without necessarilydestroying the snails;

(4) Biocidal rubber compositions containing Bayluscide additives effecta 100% kill of the host snail of the shistosome cercariae atconcentrations of the dissolving toxic in the infested water of lessthan 1 p.p.m. within 24 hours of the immersion of the composition; thiseffect being continued in flowing water for more than nine monthswithout loss of toxic strength;

(5) The item (4) compositions effect a 100% kill of shistosome cercariaewithin minutes at concentrations of less than 10 p.p.b. of thedissolving substance or substances in the infested water;

(6) Snail hosts of the shistosome cercariae are strongly affected forperiods as long as 600 hours after contact with supposedly non-lethalconcentrations well below those given above putting in question of thelong term effects of even such microscopic concentrations and raisingquestions about accepted dosage levels of these well-known toxicants.

(7) Gravid female mosquitos are attracted by water containing theabove-listed low concentrations of organotin compounds released from abiocidal rubber;

(8) Fabric coated with a biocidal rubber of this invention kill adultmosquitos, body lice, termites, cockroaches and horsefiies coming intocontact therewith;

(9) Surfaces of the biocidal rubbers of this invention kill and prevent.growth of many pathogenic bacteria and fungi, including staphylococciand streptococci;

(10) Rabbits will not chew a biocidal rubber containing TBTO or TBTS;

(11) Rats will not gnaw such biocidal rubber compositions;

(12) woodpeckers will not penetrate such compositions;

(13) Cats, dogs, birds, bats and raccoons are repelled by coming nearsuch rubber compositions;

14) Cold weather and cold water inhibits marine fouling and killslarvae, but low temperatures have no effect on the biocidal efficiencyof these'compositions whenever warm weather returns or is encountered,as by a moving ship.

The invention will now be described with reference to several specificexamples whichare intended to be illustrative only and not as limitingthe invention.

EXAMPLE I In this example, bis (tri-n-butyl tin) oxide (TBTO") andNeoprene WRT (polychloroprene) are utilized in preparing a biocidalrubber composition of this invention. The compounding recipe is asfollows:'

1 Pheuyl beta-naphthylamine.

The above materials are mixed on a cold rubber mill by first milling therubber until a sheet forms and then adding the other materials graduallywhile continuing the milling. To the above standard formulation areadded varying amounts of TBTO added as a oily liquid. The latterdisappears rapidly and is absorbed by the rubber mix during milling. Allcompositions have good milling qualities. The resulting compositions arevulcanized for 30 or 45 minutes at 300 F. in a sheet mold. The resultingvulcanized sheets are 0.03, 0.062 or 0.125 inch in thickness and areadhered to metal panels (Hydro-Lock Cement; B. F. Goodrich Company,Akron, Ohio) which are immersed in the sea off Miami Beach, Fla., andoff Duxbury and Woods Hole, Mass. Each panel is removed from the wateronce each month for inspection with an actual count of the barnacles andbryozoans attached to each sheet, counted and noted. The results are asfollows:

Status Bryozoan TB'IO, Thick- 40th mo., Expected phr. (perness, N 0.coverage, foul-tree Code cent/wt.) in. harnacles percent life, mos.

(8. 4) 0. 062 0 6 0 (4. 38) 0. 062 0 0 (2. 9) O. 062 0 1 (1. 5) 0. 062 01 (0.75) 0. 062 0 0 (0.37) 0. 062 0 1 (0. 18) 0. 062 1 CF 35 0.125 0.062CF CF 0. O6 0. 062 9 CF 9 CF 12.0 0. 125 0 0 4. 0 O. 125 0 0 1.0 0. 1250 10 0.25 0. 125 40 17 0.06 0.125 CF CF 6. 0 0. 032 0 2. 0 0.032 0 0. 50. 032 2 1 According to residual tin analysis. 7 Completely fouled.

Months to first appearance Thickness, TBTO,

in. phr. Algae Barnacles CF 1 V32 12 17 y a 12 2Q l- 12 $52 4. 0 $1 a 4.O M; 4. 0 )z 1. 0 7 13 19 M e 1. 0 6 12 17 1. 0 10 18 23 $52 0. 25 2 3 8H a 0. 25 2 4 5 0. 6 2 20 1 CF" means completely fouled.

Those not completely fouled (CF) continue unfouled at 42 months. Fromthese and other data, it appears that long extended antifouling actionwith organotin toxicants requires a thickness of at least about'0.05inch and an organotin loading of at least about 2 phr.

Results similar to those obtained on immersion "off Miami are achievedoff Bimini, B.W.I.; Kaneoha Bay, Hawaii; Seattle, Wash.; and Long Beach,Calif.

EXAMPLE II In another warm water test off Miami, similar /S-lHCh. panelscontaining 6 to 12 phr. of TBTO show very extended no-fouling life. Inone such panel bis(tributyl tin) sulfide (TBTS) is substituted for TBTO.Core type samples removed from such panels are analyzed for residual tincontent as a basis for a Predicted Foul-free Life. The data are:

Months Months ul-iree predicted at last foul-free Toxieant Phr. reportlife These results exceed the best performance of the best antifoulingpaints by a factor of 4 to 6 or more and at organotin loadings /5 to /3those of the paints.

As indicated above, antifouling life predictions are based on residualtin analyses. Below are shown a typical series of analyses on oneneoprene panel which contained about 12 phr. of TBTO (corresponds to3.52% /wt. of tin, as tin); the data are:

Percent/wt.

Months immersed: residual tin 0 3.52

Barnacles begin to attach when the residual tin concentration falls toabout 0.04 to 0.05%/wt. Algae growth commences when the residual tincontent has fallen to about 0.1%/wt.

Similar formulations based on neoprene but. employing HAF carbon blackare prepared with various levels of. either TBTO or TBTS. The recipe isas follows:

Etlwlmm tliiourcn.

The above formulations are cured for 15 minutes at 307 F. in the form ofsheets 0.075 inch thick. Panels are prepared as indicated and immersedoff Miami, Fla. The data are as follows:

Months to (average) In the above data and elsewhere herein, where novalue is given immersion testing continues on foul-free panels. Based onthe above data, it appears that the 29.6 phr. of carbon black wassomewhat too high for the panels containing only 1 to 3% toxicant.Panels containing 4 phr. or more of toxicant are excellent antifoulingmaterials. TBTS is shown to be as effective or more elfective than TBTO.

Because the compositions of Example II did not exhibit as long afoul-free life as those of Example I of comparable TBTO level, it isdecided to evaluate the effect of the type of carbon black on theantifouling efficiency of neoprene formulations. Separate compositionsare prepared from each of a number of commerciallyavailable carbonblacks according to the procedure and recipe of Example I. Test panelsare then prepared and immersed at Miami, Fla. To reduce the test time,only 0.72% /wt. (1 phr.) of TBTO is employed. In the data below, thecarbon black is identified by commercial-type designation, ultimateparticle size and typical oil absorptivity values.

Oil Five-month Particle absorptivlty, fouling Carbon black type sizegals/100 lbs. performance None.

Do. Do. Fouling month IV. Fouling month III. Foulljng month II.

Month to Phr.-ISAF carbon black: 1st barnacle These data indicate thatthe shorter antifouling noted in Example II is due to too high a levelof carbon black at this low TBTO level. Apparently, TBTO diffusion rates:at the higher black loadings are too low at this low level of TBTO tomaintain an .antifouling surface.

In case that the cure .conditions in tht above experiments were gnpt.cprre ct still another series of formula- 16 tions are prepared, allemploying 14.5 phr. of ISAF carbon black, 0.25 phr. of TBTO and allcured at 300 Fv but for differing periods of time. The data belowdemonstrate the antifouling behavior of test panels immersed for sixmonths at Miami, Fla:

Month Six mouth to 1st observationbarnucle n0 barnacles Cure time,minutes Do. 2 barnaclcs. l barnacle. 3 barnaclcs. 1 barnaelc. 2Obarnacles. 5 barnaclcs.

The above data indicate that a cure of 20 to 30 minutes at 300 F.produces markedly better antifouling behavior than even moderatelyovercured panels which are cured 45-60 minutes.

EXAMPLE III Months to appearance of:

Wax 1 Foul-free Code loading Algae Barnacles lite, mos.

None 32 89 39 1 Antlsun wax, specific gravlty=0.92.

I By residual tin analysis.

The use of 2 to 5 phr. of wax is seen to exhibit a rather strong effecton the foul-free life. A foul-free life of nearly five years insubtropical coastal waters is at least three times or more better thanthat of the very best antifouling paints.

EXAMPLE IV In a similar fashion, panels are prepared based on naturalrubber and employing TBTO or TBTS. The general recipe and cure cycleemployed is:

Material: Phr. Natural rubber HAF carbon black l 40 PBNA l ZnO 5 Stearicacid 3 MBTS 0.6 Sulfur 2.5

The material is cured for 15 minutes at 307 F. in the form of sheets 6"x 6" x 0.075" which are adhered with adhesive to polyvinyl chloridesubstrates to insure contact of only one surface with sea water.Immersion is off Miami, Fla, for 35 months to date of last report. Thedata obtained are:

Toxlcant Month to (average 2 to 6 panels) 1% 1 barn- 50 barn- Type Phr.algae acle ncles CF 0 1 l 1 l 'IB'IO 1 ll 13 15 18 TBTO 3 l8 lti 20 21TBTO 5 2'] 2'2 24 23 'IBTO 8 26 '26.. H... TBTS 2 8 11 19 19 TBTS 4 2013 21 23 TBTS 6 20 2'2 '23 '23 TBTS 8 21 20 17 The above data indicatethat natural rubber compounds lose toxicant relatively faster than doesneoprene and the use of about 50 phr. of carbon black and/or 2 to 5 phr.of wax would slow such loss and produce longer-lived antifoulingcoatings. Of the panels remaining on test after 35 months, thosecontaining phr. of TBTS appear to be very good antifouling materials.Nevertheless, the panels containing 5 to 6 phr. or more of eithertoxicant are good for approximately 2 years or more under extremelysevere semi-tropical coastal fouling conditions.

EXAMPLE V In this example, a series of panels each containing 10 phr. ofTBTS are prepared each from a different elastomer, including severalnitrile rubbers known as Hycar 1043 (butadiene/acrylonitrile copolymercontaining about 34% /wt. combined acrylonitrile) and Hycar 1001(similar but containing about 38 to 40% /wt. combined acrylonitrile) andHycar 1014 (similar but containing about 18%/wt. combined acrylonitrile;all products of The B. F. Goodrich Chemical Company, Cleveland, Ohio);SBR rubbers 1001, 1013 and 1015; Ameripol CB, a cis-l, 4-polybutadienerubber made by Goodrich- Gulf Chemicals, Inc., Cleveland, Ohio; butylrubber; and EPDM rubber (Nordel 1070, Du Pont). The recipes, other thanthose for neoprene and natural rubber which are given in the Examplesabove, are as follows:

SBR Butyl EPDM Hycar 1 Contains also 50 phr. Flexon 76, processing oil.

2 Santoeure", N-eyclohexyl-2-benzothlazylsulfeuamlde. 8 minutes at 307F.

4 minutes at 307 F.

l 60 minutes at 307 F.

The materials are mixed on a rubber mill and molded into sheets 6" x 6"x 0.075" thick which are adhered by a suitable adhesive to either astainless steel or polyvinyl chloride backing. The panels so preparedare immersed off Miami, Fla., and the data taken for months. The dataare summarized as follows in order of antifouling efficiency and life:

Months to:

1 bar- Rank Elastomer base nacle CF 1 Hycar 1043 35+ 35+ 2 Hycar 10 3036+ 3 Natural r 29 36+ SB R 1013 29 35+ All of these formulationsoutperform the best antifouling paints by a considerable margin.

EXAMPLE VI In this example, several organo-tin compounds are evaluatedin place of TBTO and TBTS. These are tributyl tin acetate (TBTA),triphenyl tin chloride (TPTC), and tributyl tin fluoride (TBTF"). Inaddition, Bayluscide (Z-ethanolamine salt of 2,5-dichloro- 4-nitrosalicylanilide) and phenyl mercury oleate (PMO) are evaluated asantifoulants. All are employed in a neoprene formulation similar to thatof Example I. These are prepared as panels having a rubber layer .03

to .062 inch thick and they are immersed off Miami, Fla. The data aresummarized as follows:

Toxicant Thickness,

inches Barnacle fouling None at 35 mos.

None at 21 mos.

Fouling commences 20th mos.

No fouling at 35 mos.

Fouled at 22 mos.

EXAMPLE VI-I In a similar fashion, panels based on Polysar 301" butylrubber (Polymer Corp., Ltd., Sarnia, Ontario) are prepared. The basicrecipe employed is:

Material: Butyl-phr. Rubber ZnO 5 Stearic acid 3 MBTS 0.5

TMTD 1.0

Sulfur 2.0 EPC carbon black 50 Cure, 25 at 307 F.

Panels immersed off Miami yield the following data:

Months immersion Toxicant (fouHree) Predicted Code Type Phr To date life1 390B TB'IO 6. 5 34 55 431A-.- TBTO 8. 6 35+ 65 'IBIO 12. 5 35+ 76 TBIO20 35+ 96 1 By residual tln analysis.

All of the above panels showed excellent retention of physicalproperties as well as foul-free performance of three years or more and apredicted foul-free life exceeding 4 or 5 years. Butyl rubber at theseloadings forms excellent, long-life antifouling materials becausephysical properties (i.e. integrity of rubber) decline quite slowly onimmersion.

EXAMPLE VIII in 600 ml. of dechlorinated water for 24 to 27 hours andthen removed before adding the snails. The concentration of toxicant inthe stock solution is not shown but equilibrium solubilityconcentrations probably are not reached. :In all cases, 100% kills ofthe snails are achieved in 24 hours or less.

' EXAMPLE IX A small quantity of the solution obtained from the 8 phr.TBTO in neoprene of Example VIII is transferred by pipette into watchglasses containing shistosome cercariae in various quantities ofdistilled water. Based on the estimated TBTO diffusion rate on long termimmersion in sea water, the initial concentration in each watch glass isof the order of 0.1 ppm. at most and of the order of 1 part per billionat the low end. Kills are 100% over the entire range and death occursalmost immediately or within a very few minutes after adding the TBTOcontaining solution.

. 19 EXAMPLE X Observations after Solution 5 min. 30 min. 60 min.

Fullstrength A1ldead Same Same. Diluted 10 times. Active Littleactivity"-.. Inactive. Diluted 100 times do Active Active.

From the foregoing, it appears that the biocidal neoprene formulationwill in 48 hours or less impart to water in contact therewith theability to kill shistosome cercariae fiukes in a matter of minutes.These results appear to have been obtained at 0.1 to 1 p.p.m. or less.

EXAMPLE XI Different biocidal rubbers, all based on neoprene but eachcontaining various loadings of various organotin toxicants, of anorgano-mercury compound and of Bayluscide are evaluated against snails.The procedure of Example Vl II is followed (except no running watertreatment). The stock solutions are diluted by 10, 100 and 1,000. Snailsare placed in a cardboard box lined with polyvinyl chloride film; thesnails conditioned 24 hours with nontoxic water; and then the toxicwater is introduced. Except in the undiluted tests, where only twosnails are employed, five or ten live Melisoma trivolvis snails are usedin each experiment.

The data are as follows:

Gone. 1, 0.1, 0.01, .001, Code Toxlcant Phr. L+D l L+D L+D L:1:D

2+0 2+0 2+0 2+0 8 0+2 0+5 3+2 4+]. 12 0+2 0+5 2+3 +0 0+2 0+5 5+0 4+1 6.5 0+2 0+5 5+0 5+0 6. 0 0+2 0+5 0+5 4+1 8. 0 0+2 5+0 5+0 5+0 1. 0 0+2 0+55+0 5+0 805B ..do 6.0 0+2 0+l0 10+0 10+0 633A Bayluselde. 8. 0 0+2 0+65+0 5+0 TBTOHH 3.0 350A TPTC l0 0+2 0+5 5+0 5+0 2 Phenyl mercury oleate.

3 Trlbutyl tln reslnate, made by M & T Chem. Co. 4 Tripropyl tinchloride.

It appears that very low dilutions of 0.1 to 1 p.p.m. are sufficient tokill snails.

These and other similar data are confirmed on field testing. Samples ofsome of the same rubbers above (443A, 633A, 895A and 895B) are placed inrunning water for 9 months and then the above procedure is repeated. Thedata on 24 hour observation are Concentration or dilution The above dataindicates the biocidal neoprene formulations would be active andeffective against snails in infested water for 9 months or more and atvery low concentrations.

EXAMPLE XII In this example, a series of biocidal natural rubbercompositions are prepared using the general recipe and cure cycle ofExample IV except for variation in the TBTO content and by substitutingvarious fatty acids for Fatty acid TBTO, LCioo Code Type Phr phr (max.)

300E Olelc 2 1.0 2 300II Palmitic 1 1.0 15.1 300F. Olelc 6 4.0 0.05300D..." Lauric.... 4 6.0 2.0 3003' Palmitic. 3 6. 0 0. 25 300A L 4 8.0 1. 5 300B 6 8. 0 1.3 3000 8 12. 0 0. 35 300G 8 12. 0 0. 09 300K.Palmltic. 8 12.0 0. 00

l 24 hour exposure.

Several of the stock solutions employed 'in the foregoing examples areallowed to stand 21 days before the foregoing snail tests .are repeated.This is to demonstrate the persistence or stability of the dissolvedtoxicant. The data are:

Dilution factor Code Toxlcant Phr. 0.1 0. 05 0.01 0.005 0.001

300C 'IBIO 12 0+20 0+20 17+3 16+4 300K. TBIO 12 0+20 9+11 19+1 300] TBTOltH-l 19+1 300G 'IB'I 15+6 17+3 633A.. Baylusclde. 17+3 IT- -3 No'rE.19+1" taken as normal mortality.

It is clear that both Bayluscide and a TBTO-X (material believedreleased from a fatty acid containing vulcanizate) retain considerablepotency. Of the two, the TBTO-X material appears most resistant tohydrolysis or other change on standing in water. Apparently, palmiticacid is the most effective in a biocidal sense.

EXAMPLE XIII In this example, the time for water in contact with thebiocidal neoprene/TBTO composition of the preceding examples to reachlethal concentrations is evaluated. In this test, 20 sq. cm. of therubber are added to 600 ml. of dechlorinated water along with 10 snails(Helisoma rrivolvz's). The data are as follows:

Hours to reach 633A 3000 300G 3001 300K 351B 443A Observed effect (1)Partial retraction (2) Full retraction 24 7 7 9 9 9 7 (3) Moribund... 268 9 9 9 10 9 (4) Dead 27 10 10 1O 10 12 11 The biocidal rubbers appearto exert their lethal effects in a very short period of hours. In theabove and other simliar series of tests we have sometimes noted anabnormally high mortality among snails which were counted as havingsurvived the 24-hour observation period indicating that 24 hours is tooshort to represent a true test of lethal dosages. Abnormally high snailmortalities have been observed for as many as days after exposure.

In a similar series of tests where varying total surface area ofbiocidal rubber is varied, it is noted that the rapidity of kill dependson the rubber surface area exposed. These and similar tests wherein asingle piece of sheet-like rubber is employed, indicate that smallerquantities require longer exposure time. Rubber in a physical formhaving a higher surface/volume ratio are more efficient and kill snailseven more rapidly than is indicated above.

EXAMPLE XIV In this example, biocidal rubbers are evaluated againstmosquito larvae (Culex pipiens). The biocidal rubber em- 21 ployed isthe formulation of Example I containing 6.5 phr. of TBTO in neoprene.Various quantities of the rubber are placed in water with a known numberof live mosquito larvae. Mortality counts are taken over various 22 Acheese cloth prevents direct contact of the larvae with rubber specimen.The mortality count is taken over a 4- day period, all larvae seinedout, and a new batch of 50 unexposed larvae added. Repeated cycles ofthis type are periods of time, depending on concentration. The data arecarried out for a total of about 42 days. The data on the summarizedbelow: first cycle are representative:

ase Toxicant Accumulative mortality (percent) after- Code elastomer TypePhr. 0 day 1 day 2 days 3 days 4 days 345B Neoprene. PMO 0 0 0 90 10350A do 'IPIC s 0 0 0 10% 351B do TBTO 12 0 0 0 20 100 378A Hycar. TB'IO6.5 0 0 0 50 100 389A Neoprene. TBTO 7.0 0 0 0 0 100 Butyl 'IB'IO 6.5 00 0 20 100 Neoprene- TBTAd 8.0 0 0 0 0 100 do 'IBTO 8.0 0 0 0 20 100 6.00 0 0 0 100 7.0 0 0 0 20 100 l Tributyltin adipate.

Dosage*:

LDm 0.5 p.p.m. 24 hours. 0.1 p.p.m 8 days. 0.03 p.p.m. 12 days. 1.0p.p.m. (pure TBTO) 24 hours.

*Calculated using diffusion rates determined by residual tin analysis oflong immersed rubber.

Similar solutions are employed as larvacides against midge and black fiylarvae. Even at 0.03 p.p.m. midge larvae succumb (100%) within 24 hours.

A ZOO-foot section of a rubber tape prepared from the aboveTBTO/neoprene composition containing 6.5 phr. (2.32% /wt. of tin) ofTBTO is secured or anchored below the surface of the water in a suburbandrainage ditch. Except for periods of high septic input, definitecontrol of mosquito larvae is observed over a span of two years. Asample of the tape removed after 8 months showed a decline in residualtin (as tin) content from 2.32% to 2.28% /wt.

EXAMPLE XV In this example, various amounts of a number of biocidalrubbers of the previous examples are evaluated against the larvae ofvarious mosquito specie. In this series, the given weight of rubber isplaced in 250 grams of dechlorinated water. The data are as follows:

All of the above biocidal rubbers are made by the recipes of theforegoing examples.

On the second cycle all but the Bayluscide rubber seemed more eflicient(due to toxicant build-up) since partial kills are observed on the 1stand second days with to 90% kills on the 3rd day and 100% on the fourthday in all cases. All organotin containing rubbers continued this typeof performance without increase or decrease for the 42-day periodindicating that the equilibrium concentration of toxicant was reached atthe end of the first cycle. Taking the code 3513 material as illustrative, the toxic-ant concentration at the end of the first 4 days isestimated to be 0.288 p.p.m. It is clear that the above tin-containingbiocidal rubbers are extremely longlived larvacides highly effectiveover long periods of exposure such as would occur in treating naturalwater courses.

EXAMPLE XVII In this example many different biocidal rubbers containingvarious organic toxicants are evaluated as to their ability to preventhatching of mosquio eggs. The procedure of the preceding example isfollowed except that eggs are substituted for larvae. The rubbers areprepared Toxicant Weight Mortality as rubber, (24 hrs.)

Species rubber Compound Phr. g. p r n Culex quin uefasciatus NeopreneCompound 8 0.37 3

D0 do TBTO 8 1.45 36 ParacriL- TBTO 5 0. 44 8 When the above quantitiesof the above rubbers are steeped for 30 days in dechlorinated water 100%kills/ 24 hours are obtained in every case. When the dead larvae areremoved and fresh larvae added 100% kills/24 hours are obtained for atotal of 45 days. Unlike some of the toxicants which are known torapidly lose potency, TBTO or TBTO-X released from vulcanized rubberdemonstrates great persistency.

EXAMPLE XVI The long term, low concentration effect of a number ofbiocidal rubbers are better demonstrated in a series wherein 18 sq. cm.of the thin sheet-like rubber are suspended by a nylon cord in thecenter of a 5 gallon glass jar containing about 10 liters ofdechlorinated water and then introducing 50 live mosquito (Culexpipz'ens) larvae.

as in the preceding examples employing the recipes and cure cycles givenand the toxicant loadings listed below:

EXAMPLE XVIII Broth cultures of various bacteria and fungi are incubatedfor 48 hours. Samples of biocidal rubber are placed on petri dishes andsubjected to steam sterilization at 15 p.s.i. for 15 minutes. Theculture broth is then pipetted into the sterilized petri dishes andculture growth observed for 48 hours.

The following organisms are employed:

Abbreviation Organism Classification AN Aspergillus niger Fungus.

Rhizopua niyriciana Do.

Staphylococcus albus Coccus gm.+. Streptococcus pyogenes Do.

Escherichia coli Baccillus gm.. Pseasomonas aerugmosa Do. Alcalz'genesfecalis" Do Aerobacter aerogenes Do Proteus vulgaris. D

Listed below are the biocidal rubbers, employed, toxicant and itsconcentration in the rubber, and organisms killed (100%/48 hours).

Toxicant Rubber Effectiveness (100% kills), code Type PHR organism No.

10513 TBTO 6.5 All, also mixtures of AN, RN,

SA, SP, EC, P. 8.0 All. 5.0 All. None None (Control).

Similarly, 100% kills are shown with all of the above organisms withrubbers containing TBTA (tributyl tin acetate), TPLA (tripropyl leadacetate), and TBTC (tripropyl-tin chloride), Abate (0,0,0,O-tetramethyl-0,0- thiodi-p-phenylene phosphoroiodate (Cyanamid), and others.

What is claimed is:

1. A biocidal elastomeric composition having a specific gravity at 25 C.greater than 1.0 and comprising a vulcanized elastomeric matrixcontaining a vulcanizable organic elastomer, from about 0.02 to about 20parts/wt. per 100 parts/wt. of said elastomer in said matrix of anorganic toxicant dissolved in such matrix, and from about to about 100parts/wt. of a high structure carbon black having an oil absorptivity ofat least 9 gals/100 lbs. per 100 parts/wt. of said elastomer in suchmatrix, said organic toxicant having a low solubility in natural waters,said matrix being vulcanized to an intermediate degree wherein the saidmatrix is in an essentially elastic condition and wherein said degree ofvulcanization and the proportion of said carbon black within theranges-stated being selected to yield a desired rate of release of saidtoxicant by said composition to its environment.

2. A composition as defined in claim 1 and further characterized by saidmatrix containing from about 1 to about 5 parts/wt. of a petroleum waxfor every 100 parts/wt. of said elastomer in said matrix.

3. A composition as defined in claim 1 and further characterized by saidorganic toxicant being selected from the class consisting of organotincompounds, organolead compounds, nitrosalicylanilide compounds, andorgano- 2'4 phosphorous compounds, said composition having at least onedimension of at least 0.05 inch.

4. A composition as defined in claim 1 and further characterized by saidcomposition containing from about 0.5 to about 10 parts/wt. of a C to Cfatty acid for every parts/wt. of said elastomer and said organictoxicant being a bis(trialkyl tin) oxide.

5. A composition as defined in claim 1 and further characterized by saidelastomer being a neoprene rubber.

6. A composition as defined in claim 1 and further characterized by saidelastomer being a butyl rubber.

7. A composition as defined in claim 1 and further characterized by saidelastomer being a butadiene acrylonitrile synthetic rubber containingfrom about 10% to about 40% wt. of combined acrylonitrile.

8. A composition as defined in claim 1 and further characterized by saidelastomer being a neoprene rubber, by said organic toxicant being abiocidally-active organotin compound and present in a proportion of fromabout 1 to about 15 parts/wt. per 100 parts/wt. of said neoprene rubber,and by said carbon black being present in a proportion of from about 10to about 35 parts/wt. for every 100 parts/wt. of said neoprene rubber insaid matrix.

9. A composition as defined in claim 1 and further characterized by saidelastomer being a neoprene rubber, by said organic toxicant being anitrosalicylanilide compound and present in a proportion of from about 1to about 15 parts/wt. of every 100 parts/wt. of said neoprene rubber,and by said carbon black being present in a proportion of from about 10to about 35 parts/wt. for every 100 parts/wt. of said neoprene rubber.

10. A composition as defined in claim 1 and further characterized bysaid elastomer being a neoprene rubber, by said organic toxicant beingan organotin compound, by said carbon black being present in aproportion of from about 10 to about 35 parts/wt. for every 100 parts/wt. of said neoprene rubber, and by said composition containing fromabout 1 to about 8 parts/wt. of palmitic acid.

11. A composition as defined in claim 1 and further characterized byhaving one dimension greater than 0.05 inch and said elastomer being aneoprene rubber, by said toxicant being bis(tributyl tin) oxide and bybeing present in a proportion of from about 1 to about 12 parts/ wt. forevery 100 parts/wt. of said neoprene rubber, and by said carbon blackbeing present in a proportion of from about 10 to about 35 parts/wt. forevery 100 parts/ wt. of said neoprene rubber.

12. A composition as defined in claim 1 and further characterized byhaving one dimension greater than 0.05 inch and said elastomer being aneoprene rubber, by said toxicant being bis(tributyl tin) sulfide and ispresent in a proportion from about 1. to about 12 parts/wt. for every100 parts/wt. of said neoprene rubber, and said carbon black beingpresent in a proportion of from about 10 to about 35 parts/wt. for every100 parts/wt. of said neoprene rubber.

13. A composition as defined in claim 1 and further characterized byhaving one dimension greater than 0.05 inch and said elastomer being abutyl rubber, by said toxicant being bis(tributyl tin) oxide and ispresent in a proportion of from about 1 to about 12 parts/wt. for every100 parts/wt. of said butyl rubber and said carbon black being presentin a proportion of from about 30 to about 55 parts/,wt. for every 100parts/wt. of said butyl rubber.

14. A composition as defined in claim 1 and further characterized byhaving one dimension greater than 0.05 inch and said elastomer being aneoprene rubber. by said toxicant being the Z-aminoethanol salt of5,2-dichloro- 4-nitrosalicylanilide and is present in a proportion offrom about 1 to about 12 parts/wt. for every 100 parts/ wt. of saidneoprene rubber and said carbon black being present in a proportion offrom about 10 to about 35 parts/wt. for every 100 parts/wt. of saidneoprene rubber.

25 26 15. A composition as defined in claim 1 and further 3,167,473 1/19-65 Ieebrick 260-41 characterized by hatving one dimension greaterthan 0.05 3,207,593 9/1965 Lunda'berry 71-66 inch and said elastomerbeing 'a butadiene acrylonitrile 3,214,279 10/1965 Scott 106-15synthetic rubber containing from about to about 3,234,032 /1966 Leebrick106-15 wt. combined acrylonitrile, by said toxicant being his (tri-3,062,720 11/ 1962 Costello 424-22 butyl tin) oxide and is present in aproportion of from 3,212,967 110/1965 McFadden et a1. 106-15 AF about 1to about 12 parts/wt. for every 100 parts/wt. of 3,239,411 3/1966Leebrick 106-15 AF said synthetic rubber, and said carbon black beingpresent in a proportion of from about 30 to about parts/ MORRIS LIEBMAN,P y Examiner wt. for every parts/wt. of said synthetic rubber. 10 S. L XAssistant Examiner References Cited US. Cl. X.R.

UNITED STATES PATENTS 106-15 AF; 260-285 B, 41.5 R;- 424 213, 230, 288,2,310,229 10/1957 Allyn 43-45 293 2,970,923 2/1961 Sparmann 106-15 15

